There have been many types and kinds of projection systems for projecting bright full color images onto a remote viewing surface. One such system utilizes three liquid crystal display panels to generate red, green, and blue monochromatic images. Each liquid crystal display has an associated color dye or pigment filter to produce each of the monochromatic images.
While such a system provides an adequate full color image, the system is relatively large in size. Thus, a bulky housing must be employed to accommodate the three liquid crystal displays so constructed and arranged for combining the monochromatic images. Furthermore, such a system is relatively expensive to manufacture, since three liquid crystal displays are employed. Thus, it is desirable to have a full color panel construction which is extremely compact in size and relatively inexpensive to manufacture, at the same time, such a panel construction should be capable of projecting bright full color images.
To reduce the size and expense of a full color projection panel construction, systems have been devised which utilize a single active matrix liquid crystal display (AMLCD). The AMLCD is comprised of a large number of monochromatic sub-pixels arranged in a triad or stripe arrangement, wherein each triad or group of three stripes forms a single full color pixel element. To produce the monochromatic sub-pixels, color dye or pigment filters are attached or deposited on the AMLCD to absorb unwanted wavelengths of light. One dye or pigment filter for each sub-pixel is required to achieve the triad or stripe full color pixel.
Although such a single panel construction has been successful in producing full color projected images, the size and efficiency of the AMLCD panel has been constricted by the physical limitations of the dye or pigment filters. In this regard, the dye or pigment filter functions by absorbing unwanted wavelengths of light and permitting a desired wavelength to pass therethrough. To accomplish this, the filters must have certain physical attributes, such as the proper thickness to absorb completely the unwanted wavelengths of light. Thus, the thickness of the filter limits the acceptable thickness of the combination of the AMLCD and the filter.
In addition to the size limitations of the dye or pigment filter, the inefficiency of the filter also detracts from its overall suitability. The absorption of unwanted wavelengths of light generates heat within the dye or pigment filter, adversely affecting its ability to absorb light. Such heat can be transmitted to the AMLCD, thereby affecting adversely the proper operation of the AMLCD which contains a heat sensitive liquid crystal material. Furthermore, dye or pigment filters are relatively hard to etch or deposit on glass during fabrication.
Therefore, it would be highly desirable to have a new and improved projection panel construction, which is relatively small in size, and yet highly efficient to produce bright full color images. Such a construction should be relatively inexpensive to manufacture.
In addition to the foregoing desirable characteristics, it would be further desirable to have such a panel construction, which can produce a high resolution image, and which at the same time can be relatively small in size.
A problem in reducing the overall size of such a panel construction has been the reduction of the pixel element aperture ratio. The aperture ratio refers to the actual area of the thin film transistor layer deposited on the AMLCD which activates the liquid crystal to modulate light passing therethrough relative to the area which does not activate the liquid crystal. The area of the thin film transistor layer which does not activate the liquid crystal is comprised of electrical circuit elements to transmit signals to the area which does activate the liquid crystal. As pixel density increases, which occurs when the size of the AMLCD is reduced, the activating area is reduced substantially in proportion to the non-activating area, thus the decrease in aperture ratio.
The reduction of the aperture ratio results in a reduction of the transmissivity of the AMLCD panel. Lower transmissivity detrimentally affects the brightness of the projected full color image. Also, cross talk can occur between the pixel elements. Thus, the image can appear to be degraded in quality.
Therefore, it would be highly desirable to have a new and improved panel construction, which is extremely compact in size, having a high density of pixel elements to produce a high resolution image. Also, such a projected image should be a bright full color image. Additionally, such a panel construction should be relatively inexpensive to manufacture.